Process for recovering zinc from zinkiferous materials.



APPLICATION FILED OCT. 7, 1913. RENEWED DEC. 3l, 1915.

Patented Feb22, 1916.

W/ 'TA/55655.'

fran l sfrafrn ra amenities cantv WILHELM rima, or HAMBURG, GERMANY.

PROCESS FOB BECOVERING'VZNC FROM ZNKIFERUS MATERIALS.

4Specication of Letters atent.

Patented Feb. 22, 1916.

Application inea october 7, i913, seriai No. 793,792. Renewed December ai, i915. serial No. cassa.

To all whom it may concern:

Be it known that I, FRIEDRICH CARL W11.- HELM T1MM, a subject of the Emperor of Germany, residing at Hamburg, Germany, have invented new and useful Improve v ments. in Processes for Recoveringy Zinc from Zinkiferous Materials, of which the following is a specification.

This invention relates to a process for blowing zinkiferous' materials which contain'the Zinc in the form ofoxid, sulfd,

silicate, or other coinpound,inorder to sep the like. rSuch additional materials assistv a good sinter, when the y in producing either pure zinkiferous materials are too strong for sintering `or are vinclined to smelt at the reaction temperature; or assist in producing a greater yield of .zincfor example by adding a. basic substance such as lime instead i- 'if another base (zinc oxid) to be driven off.

Y disadvantage, prsent It is known in the art to provide admixtures of appropriate substances to the zinkiferous materials, that are to be deprived of their Zinc by ordinary blowing. Tle blowing consists of treating by means of air or gases containing free oxygen conducted through the charge, thereby producing internal combustion. The said air or gas containing free oxygen is conducted through the charge for a comparatively short time which only suflices for burning a portionrof the fuel. The charge is then removed from the grate or bther; sustaining device, land is again de posited on the same' or another grate or support, f l is then again blown and removes as before in such a manner that the blowing is carried out intermittently, to the greatest possible or to the desiredV degree of dezinkiication, on a charge periodically deposited on the grate or. support and afterward removed therefrom. The air or other gas used may be conducted through the charge from below upward or in the reverse direction.

'The process 'is intended to overcome the in the method usually s employed hitherto, of dezinkiiication by e blowing, namely, that owing to the combustion ofthe fuel the furnace charge shrinks very much and settles irregularly, in conthrough the gaps, and therefore only pass aroundthe more ldensely lying portions and there give up their heat less effectually, and drive out the zinc less completely. lf, for example, a mixture consistingv of two parts by weight of ore and one part of coke breeze is blown in a converter which expands toward the top, then the charge hangs in the furnace soon after the blowing has commenced. For in this case the relative lvolumes of ore and coke are about as 1:2,

, sequenceof which the gases escape mostly I tion. On blowing in a downward direction irregularities in thev even distribution 'of the draft also occur owing to the sinking down ofthe charge at only some parts of the section, and this effect is more marked the greater the space taken up by the fuel. In working according to the present process, however, the charge is not blown long enough for the empty space arising from the disappearance ofv the fuel in the zone of combustion to cause any irregular disposition in the rest ofthe charge, the blowing being interrupted, the chargeremoved from the grateof the furnace and then deposited anew as regularly as possible on the same or another grate of the same or another furnace, and again blown. The duration and number of repetitions of the blowing are adapted ,to the nature of the materials to be treated. l

It is sometimes specially desirable to make each period of blowing so short that no largecoinpact lumps of sinter are formed. By blowing for only a short period, the hot and softresidue (poor in zinc) of the zone of combustion is broken comparatively easily by removing ,the charge from the grate; and when mixed with the iest of the charge may be distributed therein in such a y manner that the charge on the grate will have about the same temperature from the top to the bottom' and therefore will easily give ofi the zinc in the next blowing period.

The process may be carried on for example in a converter of the kind illustrated in vertical section in the drawing.

A is the blowing space, B1 B., the hollow trunnions, C the air admission pipe v(stationary), D the gas eduction pipe (stationi ary), E the opening for charging the heating materials and charge, F the grate, and G a spur-wheel serving for the rotation of the converter by means of gearing. i

Red-hot coke is first introduced from above through the opening E on to the grate F.A The preferably already preheated charge is then put in, (say previously roasted poor zinc-blende mixed with small coalor coke) and the opening E is closed- By the admission of a small quantity of air the temperature is then so far increased that zinc is evolved from thecharge. This zinc passes ofl' with the products of combustion through one of the trunnions, either as vapor, as oXid, or as a mixture of both, accord ing to' the purpose required, and to the conditions selected therefor. But after a short time 4thedraft is vcut off, and the converter is then turned once or several times about its axis, whereby the contents are mixed up. The same effect may be obtained by an oscillating movement of suflicient amplitude. i In order to obtain a layer of even thick'- ness, the movement of the converter is stopped when the surface of its grate has about the same inclination as the angle of repose of the charge in its interior. Then the converter is turned back-in the opposite direction until the surface of the charge is 4evenly distributed over the grate and consequently offers a like resistance lto the blast at every part of the grate. Itis then again blown for a short time, mixed anew, and these 'processes are continued alternately until the contents are sufficiently poor in zinc, when they are emptied out through the opening E.

Instead of treating a charge as described intermittently in a converter of the kind described or in asimilar apparatus by a series of blowing periods and thus decreasingthe vZinc content from the highest to the lowest grade, the method of working may be made continuous, or approximately continuous, by using a comparativelylong converter of the shape of a drum or of a rotary furnace, at one end of which the charge .is introduced as regularly as possible, andv at the other end of which the dezinkiied materials are extracted.` The' grate in such a long converter extends parallel to the 'axis and is of fair length but comparatively-,narrow in width. The charge travels through the converter,

whole a little downward, this being caused r ,by the inclination of the furnace.

After a certain number of blowing periods, and consequently of revolutions, the material will be moved from the, inlet to the outlet and is practically free from zinc. In such a long converter there is always a change of zinkiferous materials, and it is not neces,

sary to clean it out before a fresh chargeis introduced- Further instead of the periodical evolution described the stream of gas and the separation of Zinc may be'rendered still more continuous, by arranging several grate surfaces 4on the inner circumferential surface, which onbeing suiiiciently covered with the charge are at the right moment put into connection with the air admission oon-.v

duit, and disconnected therefrom as soon as (by the rotation or oscillation of the converter) they are no longer sufficiently covered.

It may also be mentioned that very fine material maybe previously briqueted or made into lumps` by some suitable method. In this case larger lumps are preferably made smaller before delivery into the furnace. Further the mixture of the Zinkiferous materials with fuel, reduction, and reaction materials may alsobe made in the furnace, instead of before delivery into it. Further the air, or mixture of gases containn ing oxygen which serve for* blowing is preferably heated. t

' The process renderspossible pot only the formation of zinc oxid', intelligible Without further explanation, which may be separated from the gases in the familiar manner, but also the formation of comparatively pure diluted zinc vapor, if the addition* of fuel. is made large enough for acomplete reduction of the carbon dioxid, This zinc vapor may be recovered by suitable condem sation either as metal, as .zinc dust, or as oXid by. oxidation. by the admission of oxygen or in some other form, sulfate for example, by any other suitable subsequent treatment. 1 n,

In this specification the terms blowing to blow and the like are used as compre hensive terms intended to cover a processfor the treatment of materials by means of heat produced internally in the charge to be treated and effecting same by conducting air or other suitable y gas under1 comparatively7 great difference of pressure through the charge. The difference of pressure between the entering air or gasI and exit gas may be obtained either by compressing the air or gas prior to introduction by exhausting the exit gases or by combining both means.

Claims:

1. The process for recovering zinc from zinkiferous materials which consists in caus-v ing gas containing free oxygen to pass through a hot mixture of zinkiierous materials and solid carbonaceous substances during a comparatively short time, then withdrawing the mixture fromthe eect of the gas passing through it, then reearranging the mixture in a practically even density, then causing the free oxygencontaining gas to pass again through the mixture and repeating this working whereby the zinc is freed from the zinkiferous materials in different periods, the heat produced by passgas through.

zinkiferous materials Which consists in causing air to pass in different periods through a mixture of zinc-containing materials and solid carbon-'containing materials, thereby decreasing gradually Vthe zinc content of the Y charge in different zinc-freeing periods,the

charge being between each two such periods remixedin itself and being arranged ina `practically even density, the heat being regu lated so as to .producea sintered residue.

In testimony whereof I have signed my` name to this specification in the presence of two subscribing witnesses.

FRIEDRICH CARL WILHELM TIMM.

Witnesses:

ERNEsr H. L. MUMMENHOFF,

IDA CHRIST. HAEERMANN. 

